In general, a magnetic angle sensor arrangement consists of a small permanent magnet on a rotating shaft. Magnetic field sensors detect the magnetic field of the rotating magnet and conclude back on the rotational position of the shaft.
Magnetic angle sensors are often used in safety-critical applications like steering angle measurements, brake-boost applications, clutch applications, etc., to detect the position of a rotating element. Sometimes, magnetic angle sensors are also mounted on a motor-shaft to detect the shaft-angle for motor-current-commutation.
Safety critical applications need safety-mechanisms to detect the correctness and safety reliability of the measurement signal. A common approach is to use two sensor chips in parallel, to provide a sensor redundancy. However, sensor redundancy does not identify systematic problems in the sensor product. Thus, sensor diversity may form an improved approach, using two separate sensor products, or even two separate sensor principles.
A commonly known problem for a steering angle measurement system is the reliability of the initial angle value. The correctness of this value cannot be checked during startup. Known safety mechanisms which are currently available and in use, use a “dual sensor” concept for providing sensor redundancy, or use a so called “dual die” concept for providing sensor diversity.
For a dual sensor concept, any kind of a dual-sensor principle using two separate sensor products are in use. To fulfill diversity, two different sensor principles or two different suppliers are used (e.g. AMR, GMR, TMR). A dual die approach is, for example, to reduce PCB area (PCB=Printed Circuit Board), wherein two different sensors are placed into one single chip-package. Here, two different sensor principles are also used in order to fulfill sensor diversity (see e.g. TLE5009, TLE5109).